1. Field of the Invention
The invention relates to chemisorptive compositions and more particularly relates to chemisorption compositions useful to filter gaseous vapors such as tobacco smoke and remove select chemical compounds.
2. Brief Description of the Prior Art
As is well known, tobacco smoke consists of a gaseous or vapor phase in which are suspended liquid or semi-liquid droplets or solid particles, which form the visible smoke stream. Conventional cigarette filters are formed from cellulosic fibers or convoluted creped paper formed into a cylindrical plug to remove varying proportions of the droplets passing therethrough. For the most part, they do not effectively remove gaseous molecules.
Such gaseous molecules, including hydrogen cyanide and hydrogen sulfide can be considered as gases or highly volatile liquids. In the brief period of time in which they are carried from the tobacco combustion zone to the smoker's mouth, there is relatively little time for the gases to condense into droplets. Consequently, these materials are almost entirely found in the vaporized state as they leave the smoking article and enter the smoker's mouth. The smooth and generally non-porous nature of commonly used fibrous filtering materials may capture tobacco smoke droplets, but do not present a sufficient surface area to effectively adsorb gaseous molecules.
In an attempt to improve the adsorptive properties of conventional tobacco smoke filters, various adsorbents have been proposed for ordinary filtering materials. In U.S. Pat. Nos. 3,251,365 and 3,460,543 it is disclosed that zinc oxide may be added to high surface area filter supports such as charcoal or activated alumina for a smoking article. Such high surface area adsorbents have an adverse effect on taste; i.e., they remove flavor compounds in addition to hydrogen cyanide and hydrogen sulfide.
U.S. Pat. No. 4,022,223 also teaches the use of alumina and activated alumina as base materials in absorptive filter compositions. Furthermore, U.S. Pat. No. 4,022,223 teaches active alumina--polyethyleneimine complexes with other ingredients.
In the U.S. Pat. No. 3,403,690 disclosure is made of filters for tobacco smoke which comprise fibrous, filamentary or sheet tobacco smoke filtering material treated with nine salts including zinc acetate. The filters have enhanced efficiency for removing hydrogen sulfide and hydrogen cyanide.
In U.S. Pat. No. 3,550,600, zinc acetate is combined with a base such as polyethyleneimine in a tobacco smoke filter support. The presence of the polyethyleneimine is said to improve the efficiency in removal of hydrogen sulfide, hydrogen cyanide and steam volatile phenols.
Polyethyleneimine has also been used on filter supports alone; see U.S. Pat. Nos. 3,340,879 and 3,716,063 (the latter using polyethyleneimine buffered with acetic acid).
Other teachings representative of the prior art are the disclosures of U.S. Pat. Nos. 3,618,619; 3,716,500; 3,802,441; and 3,898,322.
In general, the prior art absorptive or chemisorptive compositions useful to filter tobacco smokes are effective in removing one or more undesirable chemicals from tobacco smoke, such as hydrogen cyanide or aldehydes. However, the prior art compositions are generally not efficient in removing large quantities of a broad variety of different undesirable smoke components simultaneously. The compositions of the present invention are efficient in removing hydrogen sulfide, hydrogen cyanide and acetaldehyde in large quantities, simultaneously. Unexpectedly, when the compositions of the invention are associated with smoking products such as cigarettes and the like, the quality of the smoking, i.e., taste, is improved.